Electrochemical device and gas storage apparatus

ABSTRACT

The present invention relates to a gas pressure regulator including an electrochemical cell ( 4 ) having a first electrode ( 1 ) for decomposing gas into ions, a second electrode ( 2 ) for converting the ions generated in the first electrode ( 1 ) into the gas again and an ion conductor ( 3 ) sandwiched in between both the electrodes ( 1 ) and ( 2 ); and a high pressure vessel ( 5 ) disposed in one side of the electrochemical cell ( 4 ). In this device, the gas is decomposed into the ions in the first electrode ( 1 ). The decomposed ions are allowed to pass through the ion conductor ( 3 ) sandwiched in between the first electrode ( 1 ) and the second electrode ( 2 ) and conducted to the second electrode ( 2 ) side. The conducted ions are reconverted into the gas in the second electrode ( 2 ).

TECHNICAL FIELD

The present invention relates to a pressure reducing device, anelectrochemical device, a pressure reducing and pressurizing device, agas storage device, a gas storage assist system, and a method fordriving these devices.

This application claims a priority on the basis of Japanese PatentApplication No. 2002-009456 filed on Jan. 18, 2002 and Japanese PatentApplication No. 2002-373798 filed on Dec. 25, 2002, the entireties ofwhich are incorporated by reference herein.

BACKGROUND ART

As means for converting high pressure gas into low pressure gas, amechanical gas regulator has been hitherto widely employed. The usualgas regulator has been a mechanical device as disclosed in, forinstance, Japanese Patent Application Laid-Open No. H04-244506.

Now, according to the contents described in the Japanese PatentApplication Laid-Open No. H04-244506, the usual gas regulator will bedescribed below.

The usual gas regulator is formed as shown in FIG. 1. That is, on oneend of an inlet side of a main body case 86, an inlet pipe 87 ismounted. On the other end, an outlet port 88 is formed. To an openingpart 86 a formed on the upper surface of the main body case 86, a cover89 is fixed. Between the main body case 86 and the cover 89, theperipheral edges of a diaphragm 90 are fixed. The diaphragm 90air-tightly partitions an atmospheric pressure chamber 91 of the cover89 side and a pressure reducing chamber 92 in the case 86.

In the center of the diaphragm 90, an operating rod 93 verticallypasses. The diaphragm 90 is sandwiched in and fixed between a collarpart 93 a provided in the operating rod 93 and a nut 94 screwed to anupper end of the operating rod 93. A spring 95 is interposed between thediaphragm 90 and the cover 89 to constantly urge the diaphragm. To thelower part of the operating rod 93, the operating end of an operatinglever 96 is crosslinked so as to slide. The operating lever 96 issupported by the case 86 through a support shaft 97 so as to rotate. Anoperating end of the operating lever 96 is engaged with a valve body 98that is opposed to an end nozzle part 87 a of the inlet pipe 87 throughan operating pin 99. In the cover 89, a vent hole 89 a communicatingwith an atmospheric side is formed.

In the usual gas regulator constructed as described above, when anamount of gas consumed in a combustion device (an illustration isomitted.) is reduced to raise pressure in the pressure reducing chamber92, the diaphragm 90 overcomes the urging force of the spring 95 to bedisplaced to the atmospheric pressure chamber 91 side, raise theoperating rod 93 and rotate the operating lever 96 counterclockwise onthe support shaft 97. The valve body 98 is allowed to come near to thenozzle part 87 a. Thus, an amount of inlet of gas is decreased to lowergas pressure in the pressure reducing chamber 92. In such a way, the gaspressure in the pressure reducing chamber 92 is maintained to asubstantially constant value correspondingly to the urging force of thespring 95.

Accordingly, when high pressure gas (a gaseous material) is suppliedfrom the inlet pipe 87 side, the gas of prescribed low pressure can beobtained in the outlet port 88 side.

The usual gas regulator according to the above-described mechanicalsystem has a large form in structural point of view. Further, since theabove-described gas regulator has movable parts, an abrasion due to afriction is generated so that the life of a machine is shortened.Further, noise is undesirably generated during an operation.

Further, the usual gas regulator merely intends to reduce the pressureof gas and is only provided with a pressure reducing mechanism. Thus, apressurizing mechanism needs to be provided separately from the pressurereducing mechanism in order to apply pressure.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a new pressurereducing device, an electrochemical device, a pressure reducing andpressurizing device, a gas storage device and a gas storage assistsystem, and a method for driving these devices that can solve problemsof the usually proposed device for converting high pressure gas to lowpressure gas as described above.

It is another object of the present invention to provide a compact,durable and silent pressure reducing device, an electrochemical device,a pressure reducing and pressurizing device, a gas storage device and agas storage assist system, and a method for driving these devices.

The present invention concerns a gas pressure regulator comprising: anelectrochemical cell including a first electrode for decomposing gasinto ions, a second electrode for converting the ions generated in thefirst electrode into the gas again, and an ion conductor sandwiched inbetween both the electrodes; and a high pressure vessel disposed in oneside of the electrochemical cell.

The present invention concerns a gas pressure regulating methodcomprising: a decomposing step of decomposing gas into ions in a firstelectrode; a conducting step of conducting the decomposed ions to asecond electrode side through an ion conductor sandwiched in between thefirst electrode and the second electrode; and a converting step ofconverting the conducted ions to the gas again in the second electrode.

In the gas pressure regulator and the gas pressure regulating methodaccording to the present invention, since the decomposing step, theconducting step and the converting step are included and a mechanicalmovable part is not provided in the device, a compact, durable andsilent gas pressure regulator can be realized.

Here, when the gas pressure regulator according to the present inventionis driven, for instance, the electrochemical cell can function to reducepressure in the high pressure vessel.

The electrochemical cell functions to reduce or increase the pressure inthe high pressure vessel, so that the gas pressure regulator accordingto the present invention can operate as a pressure reducing andpressurizing device.

In these cases, since a mechanical movable part is not provided in thegas pressure regulator according to the present invention, a compact,durable and silent device can be obtained. According to the presentinvention, since one device is formed so as to have a pressure reducingmechanism and a pressure applying mechanism, a more compact device thana usual gas regulator can be realized.

In the present invention, gas is desirably in a state of gas underordinary temperature and ordinary pressure. Specifically, the gas isdesirably hydrogen gas or oxygen gas.

The ion conductor is preferably a film made of an electrolyte materialcapable of permeating ionized gas. Further, the first electrode and thesecond electrode are preferably electrode films on which a catalyst suchas platinum capable of ionic equilibrium of gas is carried.

The electrode preferably has a heat resistance and a large surface areaas much as possible. Each electrode can preferably come into tightcontact with the ion conductor over an entire surface through thecatalyst carried on a surface. The electrode preferably has flexibilityto some degree so as to come into tight contact with the ion conductor.Further, the electrode is preferably an activated electrode.

Accordingly, the first electrode and the second electrode are preferablyporous or mesh shaped. For instance, the first electrode and the secondelectrode can be formed in such a way that carbon fibers or porouscarbons are formed in a sheet shape and an active catalyst is carried ona side which comes into tight contact with the ion conductor made of thesheet shaped electrode material. To such a sheet shaped electrodematerial, a net shaped core material formed by braiding metal wires, asa core material, may be inserted or stuck. The metallic core material isinserted or stuck to the electrode so that the electric conductivity ofthe electrode itself can be improved and a uniform current distributionover an entire surface can be expected.

The catalyst is desired to be fine particles of, for instance, platinum,ruthenium oxide, iridium oxide, etc. Any other electrode materials suchas silver by which a reaction as a purpose of the present inventionproceeds may be employed.

The catalyst may be carried on the electrode by an ordinary method. Forinstance, a method may be used that a catalytic material or itsprecursor is carried on the surface of carbon powder, subjected to aprocess such as heating to form catalytic particles and the catalyticparticles are baked together with a fluororesin on the surface of theelectrode. Further, an electrode body on which the catalytic material isnot carried is previously formed. Then, a precursor of the catalyticmaterial, for instance, the mixed aqueous solution of platinic chlorideand ruthenium chloride or butyl alcohol solution is applied to thesurface of the electrode as application liquid and sintered in areducing atmosphere including hydrogen at 200 to 350° C. Thus, an alloyof platinum and ruthenium can be formed on the surface of the electrode.

The device according to the present invention has preferably a lowpressure vessel in the other side of the electrochemical vessel. Theelectrochemical cell preferably serves as a gas partition. Means forregulating pressure by controlling a potential between both theelectrodes is preferably provided when a pressure difference isgenerated at both the sides of the electrochemical cell. Further, anelectromotive force generated from the pressure difference is preferablyshort-circuited by a relay, etc. or pressure is preferably regulated bya variable resistor.

Ordinarily, when the pressure difference is generated at both the sidesof the electrochemical cell, the electromotive force is generated fromthe pressure difference. This is known as the formula of Nernstincluding the term of pressure shown in a below-described formula.E=E ₀+(RT/2F)ln(P1/P2)  (1)

In the formula (1), E₀ represents an ionized potential of gas, Rrepresents a gas constant, T represents a temperature, F represents aFaraday constant, and P1 and P2 represent gas pressure.

Essentially, when the gas pressure is the same at both the sides of theelectrochemical cell as the partition wall, a potential difference isnot generated. However, when gas pressure in one side is raised, theelectromotive force due to the term of ln(P1/P2) in the formula (1) isgenerated.

For instance, when the gas is hydrogen gas, equilibrium as shown by abelow-described formula (2) exists on the catalyst such as platinumcarried on the electrode.H₂=2H+2e ⁻  (2)

When the pressure rises, this electrochemical equilibrium shifts tomitigate a stress. This reaction equilibrium causes a volume to bechanged, which has a very important meaning. That is, when the pressurerises, the equilibrium shifts rightward so as to mitigate it. Thus, manyelectrons flow into the electrode to raise the potential. At the sametime, many protons (H⁺) are injected to the ion conductor in the highpressure vessel side so that the protons are apt to be diffused to thelow pressure vessel side.

When the protons diffused to the low pressure vessel side are notrecombined to the electrons, the protons cannot return to the hydrogengas. Accordingly, when an electrical short-circuit in which thepotential difference between both the electrodes is constant isgenerated, the protons are recombined to the electrons in the lowpressure vessel side. Thus, apparently, the hydrogen gas flows to thelow pressure vessel side.

In this process, the gas interrupting characteristics of the ionconductor is required. As described below, for instance, when thehydrogen gas is used as the gas, a proton conductor including fullereneor the like as a base is useful for the ion conductor.

Basically, since only ions of specific gas can pass through the ionconductor, the electrochemical cell also has a function as a gasrefining filter. Accordingly, when the hydrogen gas is used as the gas,the electrochemical cell is most suitable as a regulator for supplyingthe hydrogen gas to an electrochemical device such as a fuel cell underprescribed pressure.

As described above, the essence of the present invention resides in theformula of Nernst depending on pressure, that is, the above-describedformula (1). When the pressure difference is generated between both theelectrodes, the potential of both the electrodes can be short-circuitedby a relay, etc., or the potential of both the electrodes can becontrolled by a variable resistor to regulate the pressure.

Both the sides of the electrochemical cell serving as the gas partitionwall have closed vessels. When one side serves as a high pressure gastank and the other side is connected to a gas consuming system, apressure sensor is disposed in the closed vessel in the other side. Thepressure sensor can interlock with a relay switch connected between boththe electrodes of the electrochemical cell to function to compensate forthe consumption of gas.

Still other objects of the present invention and specific advantagesobtained by the present invention will become more apparent from thedescription of embodiments explained below by referring to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a usual example of a gasregulator.

FIG. 2 is a schematic sectional view showing a pressure reducing deviceaccording to the present invention.

FIG. 3 is a graph showing a change of pressure of a high pressure vesselside of the pressure reducing device according to the present invention.

FIGS. 4A and 4B are structural views of polyhydroxylated fullereneshowing one example of a fullerene derivative usable for the presentinvention.

FIGS. 5A and 5B are schematic views showing examples of fullerenederivatives.

FIGS. 6A to 6M are schematic views showing various examples of a carboncluster as a nucleus in a proton conductor.

FIGS. 7A to 7D are schematic views respectively showing other examplesof the carbon cluster (partial fullerene structure).

FIGS. 8A to 8G are schematic views respectively showing other examples(diamond structure) of the carbon cluster.

FIGS. 9A to 9H are schematic views respectively showing still otherexamples (clusters are bonded together) of the carbon cluster.

FIGS. 10A and 10B show a carbon nanotube as the nucleus of the protonconductor, and FIG. 10C is a schematic view showing carbon fibers.

FIG. 11 is a schematic sectional view showing an electrochemical deviceaccording to the present invention.

FIG. 12 is a schematic sectional view showing a gas storage deviceaccording to the present invention.

FIG. 13 is a schematic sectional view of outlet and inlet pressuredetecting means connected to the gas storage device according to thepresent invention.

FIG. 14 is a schematic sectional view showing the gas storage deviceaccording to the present invention and a gas storage assist systemconnected thereto.

FIG. 15 is a schematic sectional view of another example of the gasstorage device according to the present invention.

FIG. 16 is a schematic sectional view of a still another example of thegas storage device according to the present invention.

FIG. 17 is a schematic sectional view showing a gas storage device inwhich an electrochemical cell is formed in a multistage structure.

FIG. 18 is a schematic sectional view of another example of the gasstorage device in which the electrochemical cell is formed in amultistage structure.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention will be described by referringto the drawings.

A pressure reducing device according to the present invention comprises,as shown in FIG. 2, an electrochemical cell 4 as a partition wall,having first and second catalytic electrodes 1 and 2 respectivelyforming first and second electrodes on which catalysts such as platinumare carried and a proton conductor 3 sandwiched in between the catalyticelectrodes 1 and 2, and a high pressure vessel 5 and a low pressurevessel 6 disposed at both the sides of the electrochemical cell 4. Avacuum pump 8 is connected to the high pressure vessel 5 and the lowpressure vessel 6 through a vacuum line 7. Further, an H₂ reservoir 9and a gas flow meter 10 are connected to the high pressure vessel 5 andthe low pressure vessel 6. To each of the vessels 5 and 6, leadintroducing terminals 11 and 12 are connected. To the end of the gasflow meter 10, a power generation device using hydrogen gas as fuel,whose illustration is omitted, is connected.

Firstly, valves 13, 14 and 17 were closed to open valves 15 and 16 andobtain a vacuum in the high pressure vessel 5 and the low pressurevessel 6 by using the vacuum pump 8. Then, the valves 15 and 16 wereclosed to open the valves 13 and 14 and introduce the hydrogen gas of 10atmospheric pressure to each of the vessels 5 and 6 by the H₂ reservoir9. After that, the valves 13 and 14 were closed. Then, the valve 17 wasopened to have only the low pressure vessel 6 of 1 atm.

At this time, when a voltage difference between the lead introducingterminal 11 and 12 connected to both the ends of the electrochemicalcell 4 was measured, the voltage difference was about 100 mV.

Then, both the electrodes 1 and 2 of the electrochemical cell 4 wereshort-circuited to measure the change of pressure of the high pressurevessel 5. FIG. 3 is a graph showing the change of pressure of the highpressure vessel 5 with the lapse of time. As shown in FIG. 3, it wasrecognized that the pressure in the high pressure vessel 5 decreasedwith the lapse of time t and the short-circuit between both theelectrodes 1 and 2 by a relay functioned.

The proton conductor 3 is desirably composed of a derivative formed insuch a way that a material made of at least one kind selected from agroup including fullerene molecules, a cluster having carbons as a maincomponent and a tubular or linear carbon structural body is prepared asa main component and a proton dissociation group is introduced to carbonatoms forming the material. Other inventions described below are thesame as the above.

Here, the proton dissociation group means a functional group in whichprotons can be separated in accordance with an electrolyticdissociation. The dissociation of the protons means that the protons areseparated from the functional group in accordance with the electrolyticdissociation.

The fullerene molecules as a nucleus of an object to which the protondissociation group is introduced may be any spherical shell type clustermolecules Cm (m indicates a natural number in which Cm may form aspherical shell structure.) without a special limitation. Ordinarily, asingle material of fullerene molecules selected from C36, C60, C70, C76,C78, C80, C82, C84, C86, C88, C90, C92, C94, C96, etc. or the mixture oftwo kinds or more materials of them is preferably employed.

The fullerene molecules were found in the mass spectrometry spectrum ofa cluster beam of carbons by a laser ablation in 1985 (Kroto, H. W.;Heath, J. R.; O'Brien, S. C.; Curl, R. F.; Smalley, R. E. Nature 1985.318, 162.). Actually, a producing method was established five yearslater. In 1990, a producing method of a carbon electrode by an arcdischarge method was found in 1990. Then, fullerene has been paidattention to as a carbon semiconductor material or the like since then.

As shown in FIGS. 4A and 4B, as Fullerenol having a structure formed byadding a plurality of hydroxyl groups to fullerene molecules, asynthesized example was firstly reported by Chiang et al. in 1992(Chiang, L. Y.; Swirczewski, J. W.; Hsu, C. S.; Chowdhury, S. K.;Cameron, S.; Creegan, K., J. Chem. Soc, Chem. Commun. 1992, 1791).

When the inventors of the present invention used the fullerenol as anaggregate as shown in FIG. 5A to generate a mutual interaction betweenhydroxyl groups of the fullerenol molecules (in the drawing, ∘represents a fullerene molecule.) which come into close contact witheach other, they could initially recognize that the aggregate exhibitedhigh proton conductive characteristics as a macro aggregate, that is,the aggregate exhibited the dissociation characteristics of H+from thephenolic hydroxyl groups of the fullerenol molecules.

According to the present invention, the aggregate of fullerene having,for instance, a plurality of —OSO₃H groups except fullerenol can be usedas the ion conductor. Polyhydroxylated fullerene as shown in FIG. 5B inwhich an OH group is replaced by an OSO₃H group, that is,hydrogensulfate esterified fullerenol was also reported by Chiang et al.in 1994 (Chiang, L. Y.; Wang, L. Y.; Swirczewski, J. W.; Soled, S.;Cameron, S., J. Org. Cem. 1994, 59, 3960). In the hydrogensulfateesterified fullerene, one molecule may include only OSO₃H groups or mayinclude a plurality OSO₃H groups and hydroxyl groups, respectively.

When a lot of the above-described fullerenols and hydrogensulfateesterified fullerenols are aggregated, a proton conductivity shown bythem as a bulk is directly related to the movement of protons derivedfrom a large quantity of hydroxyl groups or OSO₃H groups originallyincluded in the molecules. Accordingly, the fullerenols and thehydrogensulfate esterified fullerenols can be continuously employed evenunder an atmosphere of low humidity.

The fullerene constituting the base of these molecules especially haselectrophilic characteristics, which is considered to greatly contributeto the acceleration of the electrolytic dissociation of hydrogen ionsnot only in OSO₃H groups high in acidity, but also in hydroxyl groupsand exhibits an excellent proton conductivity. Since a relatively largequantity of hydroxyl groups and OSO₃H groups can be introduced to onefullerene molecule, the density of the proton conductor related toconduction per unit volume becomes very high. Thus, a substantialconductivity is realized.

Most of the fullerenol and the hydrogensulfate esterified fullerenol arecomposed of fullerene carbon atoms, they are light and hardlydeteriorated and include no contaminated material. The production costof fullerene is being rapidly lowered. The fullerene is considered to bea substantially ideal carbon material more than any other materials fromthe viewpoints of resources, environment and economy.

Further, the proton dissociation group does not need to be limited tothe above-described hydroxyl group or the OSO₃H group.

That is, the proton dissociation group is represented by a formula —XH.X may be an arbitrary atom or an atomic group having a bivalent bond.Further, this group is represented by a formula —OH or —YOH. Y may be anarbitrary atom or an atomic group having a bivalent bond.

Specifically, as the proton dissociation group, any one of —COOH, —SO₃H,—OPO(OH)₂, and —C₆H₄—SO₃H except —OH and —OSO₃H is preferable.

To synthesize fullerenol usable in the present invention, for instance,well-known processes such as acidification or hydrolysis are suitablycombined and applied to fullerene powder, so that desired groups can beintroduced to carbon atoms forming the fullerene molecules.

Then, an obtained fullerene derivative is formed in the configuration ofa film by an application or a deposition method to be used for theproton conductor 3 of the electrochemical cell 4.

The proton conductor 3 may be substantially composed of only thefullerene derivative or the fullerene derivative may be bonded by abinding agent.

When the proton conductor 3 is substantially composed of only thefullerene derivative, a film shaped proton conductor 3 formed by moldingthe fullerene derivative under pressure may be used. When the fullerenederivative bonded by the binding agent are used as the proton conductor3, the proton conductor with an adequate strength can be formed by thebinding agent.

As polymer materials usable as the binding agent, one kind or two ormore kinds of polymers having well-known film forming characteristicsare employed. The proton conductor having such a structure can exhibitthe same proton conductivity as that of the proton conductor composed ofonly the fullerene derivative.

Further, the film forming characteristics resulting from the polymermaterials are given to the proton conductor differently from the protonconductor made of only the fullerene derivative. Thus, the protonconductor formed by bonding the fullerene derivative using the bindingagent can be used as a flexible proton conductor 3 higher in itsstrength than a compression-molded product of the powder of thefullerene derivative and having a gas permeation preventing function. Aproton conductive thin film used at this time has the thickness of 300μm or smaller.

As the polymer materials, any of materials that do not hinder theconductivity of protons (due to a reaction with the fullerenederivative) as much as possible and have film forming characteristicsmay be used without a special limitation. Ordinarily, a material havingno electronic conductivity and having a good stability is used. Asspecific examples, polyfluoroethylene, polyvinylidene fluoride,polyvinyl alcohol, etc. may be exemplified. These materials arepreferable polymer materials from reasons described below.

Firstly, since polytetrafluoroethylene can more easily form a thin filmhaving higher strength with a smaller amount of mixing than otherpolymer materials, the polytetrafluoroethylene is preferable. In thiscase, the amount of mixing is 3 wt % or less and preferably an amount assmall as 0.5 to 1.5 wt %. The thickness of the thin film can beordinarily reduced to 100 μm to 1 μm.

Polyvinylidene fluoride or polyvinyl alcohol is preferable, because theproton conductive thin film having the excellent gas permeationpreventing function can be obtained. In this case, the amount of mixingis preferably located within a range of 5 to 15 wt %.

When each of the amount of mixing of polyfluoroethylene, polyvinylidenefluoride or polyvinyl alcohol is lower than the lower limit value of theabove-described range, an adverse effect may be possibly given to a filmformation.

In order to obtain the thin film of the proton conductor formed bybonding the fullerene derivatives respectively by the binding agent, awell-known film forming method such as a pressure molding method or anextrusion molding method may be employed.

In the device according to the present invention, the electrodes 1 and 2and the fullerene derivative as the proton conductor 3 are preferablyformed in flexible sheet shapes having a physically adequate strength inview of treatment and compactness.

Since the electrochemical cell 4 can effectively function in atmosphericair, even when temperature or humidity during an operation is notadjusted, the pressure of the hydrogen gas can be efficiently reduced.

The fullerene derivative formed by introducing the proton dissociationgroup to the carbon atoms forming fullerene molecules such asfullerenols is used as a material for forming the proton conductor 3.Thus, the electrochemical cell 4 can function in the atmospheric airunder a state of low humidity even when there is no humidifier,differently from a case that Nafion as an H₃O⁺ ion conductor is used.

That is, since the pressure of the hydrogen gas can be reduced in theatmospheric air under the state of low humidity, an initial operationcan be accelerated upon reducing the pressure of hydrogen withoutrequiring a time until a steady operation. For instance, the humidifiermay be provided to similarly reduce the pressure of the hydrogen gasunder the presence of water. However, the present invention does notessentially require the above-described conditions.

When Nafion as the H₃O⁺ ion conductor is used, hydrogen is compressedand water is also generated, so that a dehumidifier is necessary. Ascompared therewith, in this embodiment of the present invention, evenwhen the dehumidifier is not provided, the pressure of the hydrogen gascan be reduced.

Further, even when the humidifier is not provided, an electrochemicalpressure reducing operation can be efficiently realized. Thus, thecontent of water of the hydrogen gas whose pressure is reduced is small.Accordingly, a dehumidifying process as a post-process can be madeunnecessary.

Therefore, the electrochemical cell 4 can efficiently reduce thepressure of the hydrogen gas. The device according to the presentinvention is more compact and highly generalized.

In the present invention, as the proton conductor, for instance, acluster derivative, can be used in place of the fullerene derivative,which is obtained in such a way that a cluster made of carbon powder isobtained by an arc discharge method of a carbon electrode, the carbonpowder is acidified and a proton (H⁺) dissociation group is introducedto the carbon powder.

Here, the cluster ordinarily means an aggregate formed by bonding oraggregating together several to several hundred atoms. The aggregateenables a proton conductivity to be improved, holds chemicalcharacteristics to have adequate film strength and is liable to easilyform a layer. This cluster indicates the aggregate that includes carbonsas main components and is formed by bonding several to several hundredcarbon atoms irrespective of kinds of carbon to carbon bonds. However,the cluster is not necessarily composed of only carbons of 100% andother atoms may be mixed therein. The aggregate that many carbons occupyincluding the above-described case is called a carbon cluster.

Since the above-described proton conductor includes, as a maincomponent, a material obtained by introducing the proton dissociationgroup to the carbon cluster as a nucleus, the proton is easilydissociated under a dry state. Thus, effects similar to those of theabove-described proton conductor as well as the proton conductivity canbe realized. Since many kinds of carbonaceous materials as describedbelow are included in the category of the above-described carboncluster, a range of selection of the carbonaceous material iseffectively wide.

In this case, the carbon cluster is used as the nucleus, because a largequantity of proton dissociation groups needs to be introduced to obtaingood proton conductivity and the above-described thing can be realizedby the carbon cluster. Thus, the acidity of a solid proton conductor isextremely high. However, the carbon cluster is hardly oxide deteriorateddifferently from other ordinary carbonaceous materials, excellent in itsdurability and component atoms are tightly bonded together. Accordingly,even when the acidity is high, the bonds between the atoms do notcollapse, that is, the carbon cluster is hardly chemically changed andcan maintain a film structure.

The proton conductor having such a structure can also exhibit the highproton conductivity even under a dry state. As shown FIGS. 6 to 9, thereare various kinds of carbon clusters. As the materials of the protonconductor, a selection range is widened.

Firstly, various kinds of carbon clusters are shown in FIGS. 6A to 6M,which include many carbon atoms aggregated and having spherical or longspherical structures or closed surface structures similar thereto. Inthis case, molecular fullerene is shown together therewith. On the otherhand, various kinds of examples of carbon clusters are shown in FIGS. 7Ato 7D, in which the spherical structures are partly deficient. Thecarbon clusters shown herein are characterized in that open ends areprovided in the structures. Most of the structures are produced asby-products in the production processes of fullerene by an arc dischargemethod. When most of the carbon atoms of the carbon cluster are bondedin SP3, various kinds of clusters having the structures of diamond areproduced as shown in FIGS. 8A to 8G. In FIGS. 7C and 7D, painted-outparts in black show a five-membered ring or a seven-membered ring.

The clusters in which the carbon atoms are substantially bonded in SP2have plane structures of graphite or all or a part of the structures offullerene or a nanotube. Since the clusters having the graphitestructures of them substantially have an electronic conductivitytherein, these clusters are not preferable as the nucleus of the protonconductor.

On the other hand, since the clusters having the SP2 bonds of fullereneor the nanotube partly include a factor of the SP3 bonds, most of themdo not have the electronic conductivity, so that these clusters havingthe SP2 bonds are preferable as the nucleus of the proton conductor.

FIGS. 9A to 9G show various kinds of cases that clusters are bondedtogether. Such structures may be applied to the present invention. InFIGS. 9A and 9B, {tilde over ()} indicates a bond chain such as (CH₂)n,(CF₂)n or the like. Further, in FIGS. 9E to 9G, painted-out parts inblack represent five-membered rings or seven-membered rings.

In the present invention, the above-described proton dissociation groupneeds to be introduced to carbon atoms forming the carbon cluster. Asmeans for introducing the proton dissociation group, a below-describedproducing method is preferable.

That is, the carbon cluster made of carbon powder is firstly produced bythe arc discharge of the carbon electrode. Subsequently, the carboncluster is acidified, or a process such as a hydrolysis is furtherperformed or a sulfonation is further performed or phosphateesterification is suitably formed. Thus, a carbon cluster derivative asa desired product can be easily obtained. In the above-describedacidifying process, sulfuric acid or the like is used.

The carbon cluster can be directly formed in the shape of a film,pellets or the like under pressure without a binder. In the presentinvention, the carbon cluster as the nucleus preferably has the lengthof a major axis of 100 nm or shorter, especially preferably 100 Å orlower and the number of groups introduced thereto is desirably 2 ormore.

As the carbon cluster, a cage type structure of fullerene or the like ora structure having open ends in at least a part thereof is preferable.Fullerene having such a defective structure has the reactivity offullerene. At the same time, the defective part, that is, the openingpart additionally has a higher reactivity. Accordingly, acid (proton)dissociation substituent groups are promoted to be introduced by theacidifying process to obtain a higher substituent introduction rate anda high proton conductivity. Further, a larger quantity of fullerene withthe above-described structure can be synthesized than ordinary fullereneand produced at an extremely low cost.

On the other hand, as the nucleus of the proton conductor of the presentinvention, the tubular or the linear carbon structure is preferablyused. As the tubular carbon structure, a tube shape, for instance, acarbon nanotube is preferably used. As the linear carbon structure, afiber type shape, for instance, a carbon fiber is preferably used.

The carbon nanotube or the carbon fiber is apt to structurally easilydischarge electrons and can greatly increase its surface area. Thus, thecarbon nanotube or the carbon fiber can more improve a protonpropagation efficiency.

Here, the preferably usable carbon nanotube or the carbon fiber can beproduced by the arc discharge method or a chemical gas phase depositionmethod (a thermal CVD method).

In the arc discharge method, a metal catalyst such as FeS, Ni, Co, etc.is used and a carbon nanotube or carbon fiber material is synthesizedunder an atmosphere of He, for instance, an atmosphere of 150 Torr byusing an arc discharge chamber. The carbon nanotube material is stuck tothe inner surface of the chamber in the shape of a cloth in accordancewith an arc discharge. Thus, for instance, the carbon nanotube can beobtained. In this case, when the catalyst coexists, the carbon nanotubehaving a small diameter can be obtained. When the arc discharge iscarried out under the condition of having no catalyst, the thick carbonnanotube having many layers can be obtained.

As described above, the carbon nanotube can be produced by, forinstance, carrying out the arc discharge under the condition of havingno catalyst. A multi-layer carbon nanotube 101 shown in FIG. 10A and amulti-layer carbon nanotube 201 with a graphene structure (a cylindricalstructure) shown in FIG. 10B is known as a high quality carbon nanotubehaving no defect and having a very high performance as an electrondischarging material.

The proton dissociation group can be introduced to the carbon nanotubeobtained as described above by the arc discharge method in the sameprocesses as mentioned above. Thus, a proton conductor excellent in itsproton conductivity even under a dry state can be obtained.

The chemical gas phase deposition method is a method for synthesizingthe carbon nanotube or the carbon fiber by allowing fine particles oftransition metals to react with hydrocarbons or CO of acetylene,benzene, ethylene, etc. A transition metal base or a coat base isallowed to react with hydrocarbon gas or CO gas to accumulate the carbonnanotube or the carbon fiber 301 on the base 300 as shown in FIG. 10C.

For instance, an Ni base 300 is disposed in an alumina tube heated at700° C. and allowed to react with toluene/H₂ gas (for instance, 100sccm) so that the carbon fiber 301 having the structure as shown in FIG.10C can be synthesized.

Here, the aspect ratio of the carbon nanotube preferably ranges from1:1000 to 1:10. Further, the aspect ratio of the carbon fiber preferablyranges from 1:5000 to 1:10. The diameter of the tubular or linear carbonstructure is preferably located within a range of 0.001 to 0.5 μm. Thelength is preferably 1 to 5 μm.

In the device according to the present invention, only the singleelectrochemical cell serving as a pressure partition wall may bedisposed. However, a plurality of electrochemical cells may be arrangedin parallel in a gas flowing direction and may have a multistagestructure. Especially, when the difference of pressure of the vesselsdisposed at both the sides of the electrochemical cell is large, severalelectrochemical cells need to be used.

The present invention concerns an electrochemical device. Theelectrochemical device comprises a pressure reducing part including anelectrochemical cell having a first electrode for decomposing hydrogengas into protons, a second electrode for converting the protons producedin the first electrode into the hydrogen gas again and a protonconductor sandwiched in between both the electrodes and a high pressurevessel disposed in the first electrode side of the electrochemical cellto accommodate a gaseous material including the hydrogen gas; theelectrochemical cell functioning to reduce pressure in the high pressurevessel; and a gas consuming part including a hydrogen gas storage partdisposed in contact with the second electrode side in the pressurereducing part, a third electrode disposed in contact with the hydrogenstorage part for decomposing the hydrogen gas supplied from the hydrogengas storage part into protons; a fourth electrode for converting theprotons generated in the third electrode into water, and a protonconductor sandwiched in between both the electrodes, the protons beingconverted into water in the fourth electrode to take out electrochemicalenergy between the third electrode and the fourth electrode.

As a method for driving the electrochemical device according to thepresent invention, for instance, when the pressure reducing part isdriven, the electrochemical cell functions to reduce pressure in thehigh pressure vessel and the hydrogen gas storage part is disposed incontact with the second electrode side in the pressure reducing part.The gas consuming part including the third electrode for decomposing thehydrogen gas supplied from the hydrogen gas storage part into protons;the fourth electrode for converting the protons generated in the thirdelectrode into water, and the proton conductor sandwiched in betweenboth the electrodes is desirably disposed in contact with the hydrogengas storage part to convert the protons into water in the fourthelectrode and take out the electrochemical energy between the thirdelectrode and the fourth electrode.

In the electrochemical device according to the present invention, sincea mechanical movable part is not provided in the electrochemical devicelike the above-described gas pressure regulator according to the presentinvention, a compact, durable and silent device can be realized.

A specific structure of the electrochemical device according to thepresent invention is shown in FIG. 11.

As shown in FIG. 11, a pressure reducing part 18 includes anelectrochemical cell 4 having a first electrode 1 for decomposinghydrogen gas into protons, a second electrode 2 for converting theprotons produced in the first electrode 1 into the hydrogen gas againand a proton conductor 3 sandwiched in between both the electrodes 1 and2, and a high pressure vessel 5 disposed in the first electrode 1 sideof the electrochemical cell 4 to accommodate a gaseous materialincluding the hydrogen gas. The electrochemical cell 4 functions toreduce pressure in the high pressure vessel 5. A hydrogen gas storagepart 19 is disposed in contact with the second electrode 2 side of thepressure reducing part 18. A gas consuming part 20 is disposed incontact with the hydrogen gas storage part 19 and includes a thirdelectrode 21 disposed in contact with the hydrogen storage part 19 fordecomposing the hydrogen gas supplied from the hydrogen gas storage part19 into protons, a fourth electrode 22 for converting the protonsgenerated in the third electrode 21 into water, and a proton conductor23 sandwiched in between both the electrodes 21 and 22. The protons canbe converted into water in the fourth electrode 22 and electrochemicalenergy can be taken out between the third electrode 21 and the fourthelectrode 22 to serve as a fuel cell part. In the surface side of thefourth electrode 22 that does not come into contact with the protonconductor 23, O₂or O₂ containing gas is supplied.

A pressure sensor 24 is disposed in the hydrogen gas storage part 19.The pressure sensor 24 serves to interlock with a relay switch 11 aconnected between lead introducing terminals 11 and 12 connected betweenthe first and second electrodes 1 and 2 of the electrochemical cell 4 tocompensate for the consumption of gas.

The high pressure vessel 5 is connected to an H₂ supply tank 25 througha valve 25 a. When pressure in the high pressure vessel 5 reaches aprescribed value or smaller, the valve 25 a is opened so that hydrogengas can be supplied from the H₂ supply tank 25. The H₂ supply tank 25may be filled with a hydrogen gas storing alloy, a hydrogen gas storingcarbon material, metal halide, etc. As the hydrogen gas storing alloys,LaNi₆, CaNi₅, TiCo0.5Mn0.5, TiCo0.5Fe0.5, TiFe0.8Ni0.15V0.05, etc. maybe employed. As the hydrogen gas storing materials, carbon materials,carbon nanotubes, carbon fibers, activated carbons, etc. may beemployed. As the metal halides, NaAlH₄, LiAliH₄, etc. may be employed.The high pressure vessel 5 may be also filled with the hydrogen gasstoring alloy, the hydrogen gas storing carbon material, the metalhalide, etc.

In this case, since the gas interrupting characteristics of the protonconductors 3 and 23 must be high, the proton conductors 3 and 23 need tohave characteristics in which ionized gas is permeated, however, gasitself is not permeated. To realize the above-described characteristics,the proton conductors 3 and 23 are desirably composed of a derivativeformed in such a way that at least one kind of material selected from agroup including fullerene molecules, a cluster having carbons as a maincomponent, and a tubular or linear carbon structure is included as amain component, and a proton dissociation group is introduced to carbonatoms forming this material in the same manner as described above.

The present invention concerns a gas storage device comprising: a gasinlet and outlet part for introducing or discharging gas; a gas storagepart for storing gas; an electrochemical cell disposed in the gasstorage part and including a first electrode for decomposing the gasinto ions, a second electrode for converting the ions generated in thefirst electrode into the gas again and an ion conductor sandwiched inbetween both the electrodes; and a pressure reducing and pressurizingpart in which the gas is supplied to or discharged from the gas storagepart through the gas inlet and outlet part in accordance with thefunction of the electrochemical cell to decrease or increase pressure inthe gas storage part.

As a method for driving the gas storage device according to the presentinvention, for instance, when the gas storage device is driven, the gasis desirably supplied to or discharged from the gas storage part throughthe gas inlet and outlet part in accordance with the function of theelectrochemical cell to decrease or increase pressure in the gas storagepart.

In the gas storage device according to the present invention, since amechanical movable part is not provided in the gas storage device likethe above-described gas pressure regulator or the electrochemical deviceaccording to the present invention, the compact and durable gas storagedevice can be realized.

A gas storage device 26 according to the present invention has astructure as shown in FIG. 12. A gas inlet and outlet part 27 providedin the gas storage device 26 has an opening for inputting and outputtinggas and a micro space sufficient for temporarily holding gas under equalpressure.

Inlet and outlet pressure detecting means 28 is provided for detectingpressure in the micro space and is, for instance, a pressure sensorusing a diaphragm. As one example of such a pressure sensor, forinstance, a pressure sensor having a diaphragm 29, a closed space 30 inwhich a prescribed quantity of gas is sealed and a micro-switch 31 asshown in FIG. 13 is used.

One surface side of the diaphragm 29 has the same pressure as that ofthe gas inlet and outlet part 27. Thus, the diaphragm 29 is moved untilthe differential pressure of the pressure of the closed space 30 and thepressure of the gas inlet and outlet part 27 is balanced to theresilient force of the diaphragm 29. When the pressure of the gas inletand outlet part 27 reaches prescribed pressure, the micro-switch 31 isswitched from ON (a connected state) to OFF (a disconnected state).

A pressure wall 32 is a pressure resistant wall for holding highpressure, for instance, 10 to 300 atmospheric pressure and has a gasmoving hole as many openings with very small areas in the boundary ofthe gas inlet and outlet part 27 and the pressure wall 32. The form ofthe pressure wall 32 is not especially limited to a specific form,however, to uniformly distribute the pressure, a cylindrical form or aspherical form is more preferable. FIG. 12 shows a sectional view takenalong a plane including the center of a cylinder when the form of thepressure wall 32 is a cylindrical form.

The gas moving hole holds a first electrode 1, an ion conductor 3 and asecond electrode 2 against the pressure of a gas storage part 33, and atthe same time, can move gas from the gas storage part 33 to the gasinlet and outlet part 27. An electrochemical cell including the firstelectrode 1, the ion conductor 3 and the second electrode 2 is apressure reducing and pressurizing part operating as independent partsand the entire part of the electrochemical cell is held in the gasstorage part 33.

Lead lines 34 and 35 are electric conductors having their one endsrespectively connected to the second electrode 2 and the first electrode1. The other ends of the lead lines are connected to a second electrodeterminal 38 and a first electrode terminal 39 while insulation from thepressure wall 32 is maintained. A connecting line 36 and a connectingline 37 connects respectively the contacts of the second electrodeterminal 38 and the first electrode terminal 39 and the micro-switch 31together.

The gas storage device 26 according to the present invention includes agas storage assist system. The gas storage assist system desirablycomprises a gas passage for supplying the gas to the gas inlet andoutlet part 27 provided in the gas storage device 26; a pressuredetecting means for detecting gas pressure in the gas passage 41; avoltage detecting means for detecting voltage generated between thefirst electrode 1 and the second electrode 2; a calculating means forcalculating a control current signal on the basis of the gas pressureand the voltage; a current supply means for generating a controlcurrent; and a switching means for alternately switching a state thatthe control current is supplied between the first electrode 1 and thesecond electrode 2 and a state that the voltage is detected until thevoltage reaches a predetermined value.

The gas storage device 26 having the gas storage assist system 40according to the present invention is shown in FIG. 14. A part shown bya broken line in FIG. 14 represents the gas storage device 26 and a partshown by a full line represents the gas storage assist system 40.

The passage 41 has a structure connected to the opening part of the gasinlet and outlet part 27 provided in the gas storage device 26 so thatgas does not leak. The gas is supplied to the passage 41 from a tank 47.

A pressure detecting mechanism 42 is means for detecting the pressurevalue of the gas in the passage 41, and, for instance, changes thedisplacement of a diaphragm to a resistance value to an analog pressurevalue of P1. The pressure detecting mechanism 42 is provided for thepurpose of detecting the pressure of the gas inlet and outlet part 27 ofthe gas storage device 26, that is, the pressure applied to the secondelectrode 2 from the gas inlet and outlet part 27 side. Since thepassage 41 is connected to the gas inlet and outlet part 27, they havethe substantially same pressure. The pressure detecting mechanism 42 isprovided in the vicinity of the passage 41, this purpose can beachieved.

A first terminal 48 and a second terminal 49 hold an electric contactwith the first electrode terminal 39 and the second electrode terminal38 of the gas storage device 26.

A switching part 46 is switching means connected to the first terminal48 and the second terminal 49 by electric conductive lines.

Contacts S0 and S1, and contacts S3 and S4 are turned on at the sametime. When a switching signal C1 is changed, contacts S0 and S2, andcontacts S3 and S5 are turned on at the same time. The switching signalC1 is transmitted from a calculating part 44. When switching members 43a and 44 a of a switch are connected to the contacts S1 and S4, apressure voltage detecting part 43 detects voltage generated between thefirst electrode 1 and the second electrode 2. When the switching members43 a and 44 a of the switch are connected to the contacts S2 and S5,prescribed current is supplied to the first terminal 48 and the secondterminal 49 from a current supply part 45.

The direction and the quantity of the current are determined by acurrent control signal C2 and the values are calculated by thecalculating part 44.

An operation upon discharging gas in the gas storage device 26 iscarried out as described below in the same manner as that of thepressure reducing device according to the present invention.

Voltage corresponding to the pressure difference between the storagepart 33 and the gas inlet and outlet part 27 is generated between thefirst electrode terminal 39 and the second electrode terminal 38 of thegas storage device 26 and guided to the respective contacts of themicro-switch 31 via the connecting line 36 and the connecting line 37.When the pressure of the gas inlet and outlet part 27 is lowered to aprescribed value or smaller, the contact of the micro-switch 31 isturned ON. Thus, current is supplied to the second electrode 2 and thefirst electrode 1 on the basis of the generated voltage and ions aresupplied to the ion conductor 3. As a result, the pressure of gas in thegas storage part 33 is reduced and the pressure reduced gas is suppliedto the gas inlet and outlet part 27. When the gas inlet and outlet part27 is sufficiently filled with the gas, the contact of the micro-switch31 is turned OFF to interrupt the current of the second electrode 2 andthe first electrode 1. Consequently, the conduction of the ions isinterrupted to stop the entry of the gas in the gas storage part 33 tothe gas inlet and outlet part 27.

As a contact form of the micro-switch 31, when a switch of a type thathysteresis characteristics, namely, different pressure allows the switchto shift to each of states of ON/OFF is used, the ON/OFF operations ofthe switch can be slowly repeated within a prescribed range of pressurechange. Thus, the life of the contact of the switch can be effectivelylengthened.

Thus, since the gas inlet and outlet part 27 is filled with gas ofprescribed pressure, the gas of the prescribed pressure can be taken outfrom an opening part. In the processes of the operation, externalelectric power is not required, so that the gas storage device high inits reliability and easy in its maintenance can be provided.

Now, an operation of the gas storage device 26 upon storing gas will bedescribed by referring to the above-described FIGS. 12 to 14.

When the gas is stored, the gas storage device 26 is connected to thegas storage assist system 40 to store the gas.

The connecting line 36 and the connecting line 37 of the gas storagedevice 26 are temporarily removed or one of the connecting lines isdisconnected by a switch which is provided halfway and is notillustrated. Then, the passage 41 is connected to the opening part ofthe gas inlet and outlet part 27, and the first terminal 48 and thesecond terminal 49 are connected to the first electrode terminal 39 andthe second electrode terminal 38.

The switching part 46 is switched to a pressure detecting operation sideby the switching signal C1 and pressure voltage is detected by thepressure voltage detecting part 43. Here, pressure in the secondelectrode 2 is detected as an output P1 from the pressure detectingmechanism 42. Accordingly, the pressure of gas in the gas storage part33 is obtained as P2 by substituting the obtained values for theabove-mentioned formula (1).

When the pressure P2 is lower than the withstanding pressure of thepressure wall 32 of the gas storage part 33, even if the gas storagepart is further filled with gas, the pressure wall 32 is not broken.Thus, the gas storage part can be further filled with the gas. To movethe gas to the gas storage part 33, the switching part 46 may beswitched by the switching signal C1 to supply current and a prescribedcurrent in an opposite direction to that of the current upon dischargingthe gas may be applied to the second electrode 2 and the first electrode1.

When the intensity of the current more increases, an amount of movementof gas more increases, so that the gas storage part can be rapidlyfilled with the gas. However, when excessive current is supplied, theion conductor 3 may be possibly broken. Therefore, the current needs tobe located within a limited range.

As the prescribed current, a constant current may be supplied throughoutall period of filling of gas, or a quantity of current may bearbitrarily controlled in accordance with the progress of the filling ofgas.

The switch of the switching part 46 is alternately switched toalternately fill the storage part 33 with gas and monitor the pressureof the storage part 33. Thus, the pressure of the gas in the storagepart 33 can be raised until prescribed pressure is finally obtained.

Thus, while the pressure of the storage part 33 is monitored withoutproviding the pressure sensor in the storage part 33, the storage part33 can be safely filled with the gas. Accordingly, the structure of thestorage part 33 can be effectively simplified. Further, in the gasstorage assist system 40 side, since a part under a high pressure statedoes not exists, the gas storage assist system 40 itself can be madeinexpensive and can be safely used in an ordinary home at the same time.

FIG. 15 shows an example in which other electrochemical cell is providedin the gas storage device 26 shown in FIG. 12. Since members designatedby the same reference numerals as those shown in FIG. 12 are the samemembers having the same operational functions, the detailed descriptionthereof is omitted.

A third electrode 21 is provided in contact with the opening part of agas inlet and outlet part 27. A second proton conductor 23 is disposedbetween the third electrode 21 and a fourth electrode 22. A thirdterminal 50 is electrically connected to the third electrode 21. Afourth terminal 51 is connected to the fourth electrode 22. An arrowmark shown by 52 indicates that liquid material or gaseous material issupplied to the fourth electrode 22.

Now, an operation of the gas storage device shown in FIG. 15 will bedescribed below.

When specific materials are supplied to the third electrode 21 and thefourth electrode 22, the gas storage device according to the presentinvention shown in FIG. 15 can serve as a fuel cell in accordance withthe actions of the third electrode 21, the proton conductor 23 and thefourth electrode 22. Here, in accordance with the materials respectivelysupplied to electrode films, the third electrode 21 serves as an anodeor a cathode and the fourth electrode 22 serves as a cathode or ananode. For instance, when hydrogen gas is supplied to the thirdelectrode 21 and air (oxygen containing gas) or oxygen gas is suppliedto the fourth electrode 22, the third electrode 21 serves as the anodeand the fourth electrode 22 serves as the cathode. Thus, negativevoltage can be obtained from the third terminal 50 and positive voltagecan be obtained from the fourth terminal 51.

The operation until the gas of prescribed pressure is obtained in thegas inlet and outlet part 27 is the same as described above.

When the positive voltage is applied to the fourth terminal 51 and thenegative voltage is applied to the third terminal 50 and pure water orwater vapor is supplied to the fourth electrode 22, the hydrogen gas canbe obtained in the gas inlet and outlet part 27. An operation that thehydrogen gas in the gas inlet and outlet part 27 is pressurized to storethe gas in the gas storage part 33 is the same as described above.

This device is a compact and portable device capable of producing gassuch as hydrogen gas and generating power. Accordingly, the device isuseful for using electric power in outdoors and for a power supply foremergency.

FIG. 16 shows a gas storage device 126 having a display part 53 fordisplaying the state of the gas storage device 26. The above-describedstate indicates, for instance, the pressure in the gas storage part 33,the filled state of the gas in the gas storage part 33, the remainingquantity of gas, or whether or not the electrochemical cell having thefirst electrode 1 and the second electrode 2 carrying catalysts forionic bond or ionic dissociation normally functions, etc.

When the pressure of the gas inlet and outlet part 27 is understood fromthe formula of Nernst represented by the above-described formula (1),the pressure of the gas storage part 33 can be recognized. When the gasstorage device 26 operates, the gas inlet and outlet part 27 ismaintained to prescribed pressure in accordance with the operation ofthe pressure detecting means 28. Thus, the pressure of the gas storagepart 33 can be grasped.

The pressure of the gas storage part 33 also shows the filled state ofthe gas in the gas storage part 33 at the same time. Since the reductionof pressure in the gas storage part 33 means the decrease of thequantity of filled gas, the filled state or the remaining quantity ofgas can be recognized thereby.

When the electrochemical cell normally operates while the deviceoperates, the micro-switch 31 provided in the pressure detecting means28 repeats ON/OFF operations. Accordingly, when the operations aredetected, it can be decided whether or not the operation of theelectrochemical cell is normal.

The display part 53 is composed of, for instance, a voltmeter or a lightemitting element such as an LED. A connecting line 54 is connected tothe second electrode 2 and a connecting line 55 is connected to thefirst electrode 1. A connecting switch 56 is connected on the waythereto. Only when the display part 53 is used, a push button 57 ispressed to connect a circuit. The display part 53 may be ordinarilydisconnected from an electrode film.

When the display part 53 is the voltmeter, the pointer of the voltmeterswings in accordance with the ON/OFF operations of the micro-switch 31.At the time of ON, since the first electrode 1 and the second electrode2 are short-circuited, the pointer of the voltmeter points zero. At thetime of OFF, voltage is generated, that is, voltage corresponding to apressure difference is generated.

Although the internal resistance of the voltmeter is high, a littlecurrent is always continuously supplied between the electrodes. Thus, avery small quantity of gas flows out from the gas storage part 33. Thus,when a display is not requested, the display part 53 is desirablydisconnected from the circuit. The display part 53 may be visuallyrecognizable detecting means such as the LED or a buzzer as meansdepending on an auditory sense. An operating point is arbitrarily set byadjusting the light emission start voltage of the LED and the pressureof the gas storage part 33 by a resistance division, or setting thespecification of winding of the buzzer.

Thus, the state of the gas storage device 26 can be displayed withoutrequiring external electric power. A refilling time can be effectivelyestimated, the remaining quantity of gas can be effectively detected andthe normal operation of the gas storage device 26 can be convenientlyrecognized.

FIG. 17 shows an example that a plurality of electrochemical cells arearranged in the gas storage device 26 to form a multistage structure.

High pressure gas is supplied to a high pressure side 58. Gas to be usedis taken out from a low pressure gas side 59. Electrochemical cells 60to 65 are arranged in such a way that empty chambers 66 to 70 arerespectively arranged between the electrochemical cells. Each of theelectrochemical cells has a proton conductor sandwiched in between twogas diffusion electrodes. A surface of the gas diffusion electrode thatcomes into contact with the proton conductor carries a catalyst.

A method for controlling each electrode of each electrochemical cell isthe same as that of the previously described embodiment, a detailedexplanation thereof is omitted.

In accordance with the device, the differential pressure at both thesides of each electrochemical cell is set to a prescribed constant valueto sequentially perform a pressure reducing operation, so that apressure difference applied to the single body of each electrochemicalcell can be reduced. For instance, when six electrochemical cells areprovided, assuming that the differential pressure applied to oneelectrochemical cell is 20 atmospheric pressure and the differentialpressure applied to the low pressure side 59 is one atmosphericpressure, the pressure of the high pressure side 58 may be 121atmospheric pressure. Irrespective of the large pressure difference suchas 120 atmospheric pressure, the pressure resisting force of theelectrochemical cell may withstand 20 atmospheric pressure. Accordingly,the design of the device is advantageously simplified.

In the device shown in FIG. 17, the empty chambers are respectivelyprovided between the electrochemical cells. However, when a function fordetecting the pressure of the empty chambers is not necessary, suchempty chambers are not necessarily required. FIG. 18 shows a schematicsectional view of a device in which empty chambers are not providedbetween electrochemical cells.

The basic structure of the electrochemical cells 71 to 76 is the same asthat shown in FIG. 17. However, gas diffusion electrodes can be commonlyused with gas diffusion electrodes of next stages. Accordingly, thenumber of the gas diffusion electrodes is decreased and the emptychambers are not provided between the electrochemical cells.

Now, an operation of this device will be described below.

Supplied hydrogen gas is electrically dissociated to electrons andprotons due to the action of a catalyst 78 carried on the surface of agas diffusion electrode 77. The electrically dissociated protons movethroughout a proton conductor due to the action of a proton conductor79. The protons are bonded to the electrons due to the action of acatalyst 81 carried on the surface of a gas diffusion electrode 80 tobecome the hydrogen gas again. The hydrogen gas is diffused in the gasdiffusion electrode 80 having many pores through which the gas passes.

The hydrogen gas permeates the gas diffusion electrode 80 according to aconcentration distribution and is electrically dissociated to theprotons and the electrons again due to the action of a catalyst 82carried on the other surface of the gas diffusion electrode 80. Theelectrically dissociated protons move due to the action of a protonconductor 83 to reach a gas diffusion electrode 84. The protons arereturned to the hydrogen gas again in the gas diffusion electrode 84 dueto the action of a catalyst 85 carried on the surface of the gasdiffusion electrode 84.

The above-described processes are repeated to sequentially reducepressure. Here, voltage is detected between the gas diffusion electrode80 and the gas diffusion electrode 84 as described above. Accordingly,for instance, when both the electrodes are conducted to each other inaccordance with the generated voltage to supply current to the gasdiffusion electrode 80 and the gas diffusion electrode 84, the pressuredifference between the gas diffusion electrode 80 and the gas diffusionelectrode 84 can be maintained to a prescribed value. The pressureresistance of the gas diffusion electrodes and the proton conductors canbe made substantially equal.

In this embodiment, an example that the hydrogen gas is used as gas isdescribed. However, oxygen gas may be used. In this case, as the ionconductor, zirconium oxide is preferably employed.

The present invention is not limited to the above-described embodimentsstated by referring to the drawings. It is apparent for a person withordinary skill in the art that various changes, substitutions orequivalence thereto may be made without departing the attached claimsand the gist thereof.

INDUSTRIAL APPLICABILITY

According to the present invention, since the mechanical movable part isnot provided in the device, the compact, durable and silent pressurereducing device, the electrochemical device, the pressure reducing andpressurizing device, the gas storage device and the gas storage assistsystem and a method for driving these devices can be realized.

The present invention is employed to make the device itself compact andportable. Thus, for instance, the electrochemical device that can becarried by an individual and can easily operate various devices drivenby using gas such as hydrogen gas can be obtained.

1. A gas pressure regulator comprising: an electrochemical cell including a first electrode for decomposing gas into ions, a second electrode for converting the ions generated in the first electrode into the gas again and an ion conductor sandwiched in between both the electrodes; and a high pressure vessel disposed in one side of the electrochemical cell.
 2. The gas pressure regulator according to claim 1, further comprising means for supplying control current to both the ends of the first electrode and the second electrode, wherein a quantity of the control current is controlled to control the flow rate of gas flowing across both the electrodes.
 3. The gas pressure regulator according to claim 1, wherein the gas is hydrogen gas or oxygen gas.
 4. The gas pressure regulator according to claim 1, wherein the ion conductor is a film made of an electrolyte material capable of permeating the ionized gas.
 5. The gas pressure regulator according to claim 1, wherein the first electrode and the second electrode are electrode films on which a catalyst capable of ionic equilibrium of the gas is carried.
 6. The gas pressure regulator according to claim 1, wherein a low pressure vessel is disposed in the other side of the electrochemical cell, the electrochemical cell serves as a gas partition wall and has a means for regulating pressure by controlling a potential between both the electrodes when a pressure difference is generated between both the sides of the electrochemical cell.
 7. The gas pressure regulator according to claim 6, wherein electromotive force generated from the pressure difference is short-circuited or the pressure is regulated by a variable resistor.
 8. The gas pressure regulator according to claim 1, wherein a plurality of electrochemical cells are arranged in parallel in a gas flowing direction and has a multistage structure.
 9. The gas pressure regulator according to claim 1, wherein when both the sides of the electrochemical cell serving as the gas partition wall have closed vessels, when one side serves as a high pressure gas tank and the other side is connected to a gas consuming system, a pressure sensor is disposed in the closed vessel in the other side and the pressure sensor interlocks with a relay switch connected between both the electrodes of the electrochemical cell to function to compensate for the consumption of gas.
 10. The gas pressure regulator according to claim 1, wherein the electrochemical cell functions as a gas refining filter.
 11. The gas pressure regulator according to claim 1, wherein the ion conductor is a proton conductor, the proton conductor is formed with a derivative by introducing a proton dissociation group to carbon atoms forming a material which has, as a main component, at least a kind of material selected from a group including fullerene molecules, a cluster having carbons as a main component and a structural body having tubular or linear carbons, and the proton generated in the first electrode is moved to the second electrode through the proton conductor.
 12. The gas pressure regulator according to claim 11, wherein the proton dissociation group is —XH (X indicates an arbitrary atom or an atomic group having bivalent bonds and H indicates a hydrogen atom.).
 13. The gas pressure regulator according to claim 12, wherein the proton dissociation group is —OH or —YOH (Y indicates an arbitrary atom or an atom group having bivalent bonds.).
 14. The gas pressure regulator according to claim 13, wherein the proton dissociation group is a group selected from any of —OH, —OSO₃H, —COOH, —SO₃H, —OPO(OH)₂, and —C₆H₄—SO₃H.
 15. The gas pressure regulator according to claim 11, wherein the fullerene molecules are spherical shell type carbon cluster molecules Cm (m indicates a natural number in which Cm may form a spherical shell structure.).
 16. An electrochemical device comprising: an electrochemical cell including a first electrode for decomposing hydrogen gas into protons, a second electrode for converting the protons generated in the first electrode into the hydrogen gas again and a proton conductor sandwiched in between both the electrodes; a high pressure vessel disposed in the first electrode side of the electrochemical cell to accommodate a gaseous material including the hydrogen gas; and a gas consuming part including a pressure reducing part in which the electrochemical cell functions to reduce pressure in the high pressure vessel, a hydrogen gas storage part disposed in contact with the second electrode side in the pressure reducing part, a third electrode disposed in contact with the hydrogen storage part to decompose the hydrogen gas supplied from the hydrogen gas storage part into protons; a fourth electrode for converting the protons generated in the third electrode into water, and a proton conductor sandwiched in between both the electrodes; the protons being converted into water in the fourth electrode to take out electrochemical energy between the third electrode and the fourth electrode.
 17. Then electrochemical device according to claim 16, wherein oxygen gas or oxygen containing gas is supplied to a surface of the fourth electrode that does not come into contact with the proton conductor to react with the protons passing through the proton conductor and convert the protons into water, and the electrochemical energy is taken out between the third electrode and the fourth electrode.
 18. A gas storage device comprising: a gas inlet and outlet part for introducing or discharging gas; a gas storage part for storing gas; and an electrochemical cell disposed in the gas storage part and including a first electrode for decomposing the gas into ions, a second electrode for converting the ions generated in the first electrode into the gas again and an ion conductor sandwiched in between both the electrodes; wherein the gas is supplied to or discharged from the gas storage part through the gas inlet and outlet part in accordance with the function of the electrochemical cell to decrease or increase pressure in the gas storage part.
 19. The gas storage device according to claim 18, further comprising: a gas storage assist system, the gas storage assist system including: a gas passage for supplying the gas to the gas inlet and outlet part provided in the gas storage device; a pressure detecting means for detecting gas pressure in the gas passage; a voltage detecting means for detecting voltage generated between the first electrode and the second electrode; a calculating means for calculating a control current signal on the basis of the gas pressure and the voltage; a current supply means for generating a control current; and a switching means for alternately switching a state that the control current is supplied between the first electrode and the second electrode and a state that the voltage is detected until the voltage reaches a predetermined value.
 20. A gas pressure regulating method comprising: a decomposing step of decomposing gas into ions in a first electrode; a conducting step of conducting the decomposed ions to a second electrode side through an ion conductor sandwiched in between the first electrode and the second electrode; and a converting step of converting the conducted ions to the gas again in the second electrode.
 21. The gas pressure regulating method according to claim 20, wherein a control current is supplied to both the ends of the first electrode and the second electrode to control a quantity of the control current so that the flow rate of gas flowing across both the electrodes.
 22. The gas pressure regulating method according to claim 20, wherein an electrochemical cell including the first electrode, the second electrode and the ion conductor serves as a gas partition wall and when a pressure difference is generated at both the sides of the electrochemical cell, a potential between both the electrodes is controlled to regulate the pressure.
 23. The gas pressure regulating method according to claim 22, wherein electromotive force generated from the pressure difference is short-circuited or the pressure is regulated by a variable resistor.
 24. The gas pressure regulating method according to claim 22, wherein when a high pressure gas storage tank is disposed at one side of the electrochemical cell serving as the gas partition wall and a closed vessel connected to a gas consuming system is disposed at the other side, a pressure sensor is disposed in the closed vessel in the other side and the pressure sensor interlocks with a relay switch connected between both the electrodes of the electrochemical cell to function to compensate for the consumption of gas. 